fix(openvpn): set default mssfix to 1320 for all providers with no default

- Partially address #2533

internal/provider/torguard/openvpnconf.go

@@ -10,6 +10,7 @@ import (
 func (p *Provider) OpenVPNConfig(connection models.Connection,
 	settings settings.OpenVPN, ipv6Supported bool,
 ) (lines []string) {
+	//nolint:mnd
 	providerSettings := utils.OpenVPNProviderSettings{
 		RemoteCertTLS: true,
 		AuthUserPass:  true,
@@ -19,7 +20,8 @@ func (p *Provider) OpenVPNConfig(connection models.Connection,
 			openvpn.AES128cbc, // For OpenVPN 2.5, see https://github.com/qdm12/gluetun/issues/2271#issuecomment-2103349935
 		},
 		Auth:         openvpn.SHA256,
-		TunMTUExtra:  32, //nolint:mnd
+		MssFix:       1320,
+		TunMTUExtra:  32,
 		KeyDirection: "1",
 		CAs: []string{
 			"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", //nolint:lll